Siloxane filter in an exhaust aftertreatment system

ABSTRACT

An exhaust aftertreatment system for an engine is provided. The exhaust aftertreatment system includes an exhaust duct, at least one of a diesel particulate filter and a diesel oxidation catalyst, a selective catalytic reduction (SCR) catalyst, and at least one siloxane filter. The at least one siloxane filter is positioned upstream of the exhaust aftertreatment system. The at least one siloxane filter is configured to filter siloxanes from exhaust gases and is structured to create a uniform distribution of siloxanes throughout the at least one siloxane filter.

TECHNICAL FIELD

The present disclosure generally relates to exhaust aftertreatmentsystems. More particularly, the present disclosure relates to a siloxanefilter in an exhaust aftertreatment system.

BACKGROUND

Landfill operations are a major part of waste management. Duringlandfill operations, waste may be delivered to landfill sites via wastecollection vehicles. After the waste is unloaded on a surface area ofthe landfill site, machines, such as compactors or bulldozers, may beused to spread and compact the waste over the surface area. The wastemay include certain domestic products that may be composed of siloxanes.The siloxanes are non-toxic silicon-bearing organic compounds that maybe added to many domestic products. Due to the widespread use of thedomestic products, siloxane concentration may gradually increase in thelandfill sites. Siloxanes are volatile compounds that evaporate andmigrate out into the ambient air. The machines that operate in thelandfill sites may be exposed to the siloxanes in the ambient air.Siloxanes may be combusted harmlessly or harmfully inside internalcombustion equipment. The siloxanes may be introduced into an engine ofthe machine via air intake and may combust to form a solid, fine silica.The silica may stick to hot surfaces inside the engine and an exhaustaftertreatment system of the engine. Also, these components may getplugged, or restrict the exhaust flow, which increases the backpressureand regeneration frequency. Additionally, sensors can be coated orplugged, causing inaccurate readings or delayed response. Therefore,high concentrations of siloxanes in the ambient air may severely affectthe maintenance intervals of the engine or machine. There may be muchmore downtime and many more parts to replace.

U.S. Pat. No. 6,365,108 discloses a siloxane filter system to protect anoxygen probe in an internal combustion engine fueled by biogases. Thefilter system includes a stainless fiber filter, which is disposed influid communication with an exhaust duct such that exhaust gases flowthrough the filter. Hence, the siloxane in the exhaust gases isdeposited on the stainless fibers of the filter and essentiallysiloxane-free gases pass over the oxygen probe. However, the filter inthe referenced patent may clog within a short period of time and hencemay require frequent replacement. This may increase the operational costof the machines engaged in landfill operations.

SUMMARY OF THE INVENTION

The present disclosure is related to an exhaust aftertreatment systemfor an engine.

In accordance with the present disclosure, the exhaust aftertreatmentsystem includes an exhaust duct, at least one of a diesel particulatefilter and a diesel oxidation catalyst, a selective catalytic reduction(SCR) catalyst, and at least one siloxane filter. The at least onesiloxane filter is positioned upstream of the exhaust aftertreatmentsystem. The at least one siloxane filter is configured to filtersiloxanes from exhaust gases and is structured to create a uniformdistribution of siloxanes throughout the at least one siloxane filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an embodiment of an engine system thatincludes an exhaust aftertreatment system, in accordance with theconcepts of the present disclosure;

FIG. 2 is a schematic of an embodiment of a siloxane filter of theexhaust aftertreatment system of FIG. 1, in accordance with the conceptsof the present disclosure;

FIG. 3 illustrates a schematic of another embodiment of a siloxanefilter of the exhaust aftertreatment system of FIG. 1, in accordancewith the concepts of the present disclosure; and

FIG. 4 illustrates a schematic of yet another embodiment of a siloxanefilter of the exhaust aftertreatment system of FIG. 1, in accordancewith the concepts of the present disclosure.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown an engine system 100. The enginesystem 100 includes an engine 102, a turbine 104, a compressor 106, andan exhaust aftertreatment system 108. The engine 102 may be of anyconventional type, such as a spark-ignited or compression-ignitedengine. The engine 102 may be used for any conventional application,such as for vehicular motive power, energy generation, or driving othermechanical equipment. The engine 102 includes combustion chambers (notshown) and is fluidly coupled to the turbine 104. The turbine 104 isoperably connected to the compressor 106 by way of a common rotatableshaft 110. The turbine 104 and the compressor 106 may be of anyconventional design, such as the axial or centrifugal-flow type. Theturbine 104 may be fluidly coupled to an exhaust manifold (not shown) ofthe engine 102, via an exhaust duct 112.

The exhaust gas is delivered to the turbine 104 via the exhaust duct112. However, a portion of the exhaust gas may be navigated to thecompressor 106. The remaining portion of the exhaust gas delivered tothe turbine 104 is navigated to the exhaust aftertreatment system 108.The exhaust aftertreatment system 108 includes one or more siloxanefilters 114, a diesel oxidation catalyst (DOC) 116, a mixing chamber118, and a selective catalytic reduction (SCR) catalyst 120. In the FIG.1, the siloxane filter 114 is positioned upstream of the DOC 116.However, the siloxane filter 114 may be positioned upstream of at leastone of the turbine 104, the DOC 116, the mixing chamber 118, and the SCRcatalyst 120. In an embodiment, the siloxane filter 114 may bepositioned downstream of at least one of the DOC 116, and the SCRcatalyst 120. The siloxane filter 114 is structured to filter and removesiloxane from the exhaust gases before the siloxane-containing exhaustgases flow to the exhaust aftertreatment system 108.

Further, the siloxane filter 114 is in fluid communication with the DOC116, therefore the filtered exhaust gas from the siloxane filter 114flows to the DOC 116. The DOC 116 is in fluid communication with themixing chamber 118, where the exhaust gas is mixed with a reductant. Theexhaust gas then flows to the SCR catalyst 120 for catalytic reduction.In an embodiment, the exhaust aftertreatment system 108 may include theone or more siloxane filters 114. The one or more siloxane filters 114may be installed anywhere in the exhaust aftertreatment system 108.Positioning of the one or more siloxane filters 114 depends on whatexhaust aftertreatment components have the potential to fail due to thesiloxane deposits. The one or more siloxane filters 114 may bepositioned upstream and/or downstream to a variety of emissionstreatment components, including, but not limited to, regenerationdevices, heat sources, oxidation catalysts, lean NOx traps (LNTs),thermocouples, pressure transducers, sensors (such as oxygen sensors,NOx sensors, ammonia sensors, soot sensors) and/or mufflers.

Referring to FIG. 2, there is shown a schematic of the siloxane filter114. The siloxane filter 114 may be composed of material, such assilicon carbide, stainless steel, polypropylene, cordierite, aluminumtitanate, mild steel, fiber, or other metallic compound known in theart. The composition material of the siloxane filter 114 is selectedbased on material qualities required to withstand engine-out exhausttemperatures and exhaust gas composition. The siloxane filter 114 may beconstructed of woven material, non-woven material, monolithicstructures, pleated material, mesh, porous supports, foams, arrays ofcells, honeycombs, or combinations thereof. Further, the siloxane filter114 may be bare or coated with a high surface area catalyst support,such as alumina The siloxane filter 114 is structured to cause siloxanein the exhaust gases to be deposited uniformly on the siloxane filter114.

The siloxane filter 114 may include a plurality of channels (not shown).The channels (not shown) may be of square, triangular, hexagonal,sinusoidal, or other shapes known in the art. The channel (not shown)may have an axial geometry, which may be uniform or tapered. However,the shape, size, and geometry of the channels (not shown) do not limitthe disclosed idea. The siloxane filter 114 may be adapted to havevaried permeability, pore size, porosity, and cells per square inch(cpsi).

The siloxane filter 114 may include a first section 200, a secondsection 202, and a third section 204. The first section 200 may bereferred to as a coarse zone. The first section 200 acts as an inletsection for an exhaust gas flow 206 to enter the siloxane filter 114.The first section 200 may be removably coupled to the second section202. The second section 202 is positioned downstream of the firstsection 200 and upstream from the third section 204. The second section202 may be referred to as a medium zone (filters finer particles thanthe first section 200). The second section 202 may be removably coupledto the third section 204. The third section 204 acts as an outletsection for the filtered exhaust gas flow, which is then navigated tothe exhaust aftertreatment system 108. The third section 204 may bereferred to as a fine zone. Each of the coarse zone, the medium zone,and the fine zone refers to pore size, porosity, permeability, or cpsiof the corresponding section of the siloxane filter 114. Hence, each ofthe first section 200, the second section 202, and the third section 204exhibit a defined porosity. The porosity of the siloxane filter 114decreases from the first section 200 to the third section 204. Thisimplies that the first section 200 (the coarse zone) has the highestporosity and the third section 204 (the fine zone) has the lowestporosity. The porosity of the second section 202 (the medium zone) liesbetween the porosity of the first section 200 and the third section 204.In an embodiment, the siloxane filter 114 may include one or moresections positioned downstream from the third section 204 and mayexhibit the porosity finer or higher than the third section 204. Theincreasingly fine porosity of the siloxane filter 114 is one way toachieve uniform siloxane distribution. Hence, the siloxane filter 114may be equipped with more sections or less sections, which continuouslyvary from coarse porosity to fine porosity. In another embodiment, thefirst section 200, the second section 202, and the third section 204 mayform a single unit, instead of being removably attached. Alternatively,the porosity of the siloxane filter 114 may continuously and uniformlytransition from coarse porosity to fine porosity.

Referring to FIG. 3, there is shown another embodiment of a siloxanefilter 300, which exhibits a tapered geometry. The siloxane filter 300may include a plurality of channels (not shown) similar to the siloxanefilter 114 (shown in FIG. 2). Further, the composition and structure ofthe siloxane filter 300 may be similar to that of the siloxane filter114 (shown in FIG. 2). The siloxane filter 300 is also structured toachieve uniform siloxane distribution. The siloxane filter 300 includesan inlet 302 and an outlet 304. The inlet 302 has a largercross-sectional area that tapers to a smaller area at the outlet 304.The exhaust gas flow 206 enters through the inlet 302, is filtered ofthe siloxanes, and exits through the outlet 304.

Referring to FIG. 4, there is shown the siloxane filter 400. Thesiloxane filter 400 may also include a plurality of channels (not shown)similar to the siloxane filter 114 (shown in FIG. 2) and the siloxanefilter 114 (shown in FIG. 3). Further, the composition and structure ofthe siloxane filter 400 is similar to that of the siloxane filter 114(shown in FIG. 2) and the siloxane filter 300 (shown in FIG. 3). Thesiloxane filter 400 includes at least one mixer 402 and a substrate 404.The mixer 402 is positioned upstream from the substrate 404. The mixer402 is adapted to create turbulence in the exhaust gas flow 206, whichenter the siloxane filter 400. The mixer 402 agitates the exhaust gasflow 206, when the exhaust gases pass through the substrate 404. Theexhaust gases are filtered across the substrate 404 and flow to theexhaust aftertreatment system 108. In an embodiment, the siloxane filter400 may be equipped with more than one mixer 402 positioned upstreamfrom the substrate 404.

INDUSTRIAL APPLICABILITY

In operation, the siloxane filter 114, 300, or 400 is positionedupstream of the components of the exhaust aftertreatment system 108, toprotect them from siloxane derived deposition damage. The siloxanefilter 114, 300, or 400 is structured to provide uniform distribution ofsiloxanes throughout the length of the channels (not shown), to minimizeback-pressure increase. The exhaust gases exit the engine 102 and flowtowards the exhaust aftertreatment system 108. Prior to entrance intothe exhaust aftertreatment system 108, the exhaust gases pass throughthe siloxane filter 114, 300, or 400, in which siloxanes are removed. Inaddition, the siloxane filter 114, 300, or 400 is functional to achievea uniform distribution of siloxanes, which increases the time betweensiloxane filter 114, changes. Further, the siloxane filter 114, 300, or400 may be configured for removal and replacement of either the entirefilter or filter elements. The disclosed idea provides increasedmaintenance intervals as compared to current siloxane filters. Currentfilter systems clog quickly and require short maintenance intervals. Thedisclosed idea may be beneficial for landfill gas engines, turbinesand/or boilers, which are required to run full time, and at fullcapacity.

Accordingly, this disclosure includes all modifications and equivalentsof the subject matter recited in the claims appended hereto as permittedby applicable law. Moreover, any combination of the described elementsin all possible variations thereof is encompassed by the disclosureunless otherwise indicated herein.

One skilled in the art will realize the disclosure may be embodied inother specific forms without departing from the disclosure or essentialcharacteristics thereof. The foregoing embodiments are therefore to beconsidered in all respects illustrative rather than limiting of thedisclosure described herein. Scope of the invention is thus indicated bythe appended claims, rather than the foregoing description, and allchanges that come within the meaning and range of equivalence of theclaims are therefore intended to be embraced therein.

What is claimed is:
 1. An exhaust aftertreatment system for an engine,the exhaust aftertreatment system including an exhaust duct, and atleast one of a diesel particulate filter, a diesel oxidation catalyst,and a selective catalytic reduction (SCR) catalyst, wherein the exhaustaftertreatment system comprises: at least one siloxane filter positionedupstream of the exhaust aftertreatment system, the at least one siloxanefilter configured to filter siloxanes from exhaust gases and structuredto create a uniform distribution of siloxanes throughout the at leastone siloxane filter.